1. Field of the Invention
Embodiments of the present invention generally relate to a system and method for sensing a position of an input object over a sensing region of a proximity sensing device.
2. Description of the Related Art
Input devices including proximity sensor devices, also commonly called touchpads or touch sensor devices, are widely used in a variety of electronic systems. A proximity sensor device typically includes a sensing region in which the proximity sensor device determines the presence, location and/or motion of one or more input objects, such as a finger. Proximity sensor devices may be used to provide interfaces for an electronic system. For example, proximity sensor devices are often used as input devices for larger computing systems, such as opaque touchpads integrated in, or peripheral to notebook or desktop computers. Proximity sensor devices are also often used in smaller computing systems, such as touch screens integrated in cellular phones. Proximity sensor devices are typically used in combination with other supporting components, such as display or input devices found in the electronic or computing system.
In some configurations, the proximity sensor devices are coupled to these supporting components to provide a desired combined function or to provide a desirable complete device package. Many commercially available proximity sensor devices utilize one electrical technique to determine the presence, location and/or motion of an input object, such as a capacitive or a resistive sensing technique. Typically, a capacitive sensing type of proximity sensor device utilizes an array of sensor electrodes and traces to detect the presence, location and/or motion of an input object. A trace is an electronic component that connects an electrode region within a sensor electrode to the controlling electronics found in the proximity sensor device.
Also, typically proximity sensor devices are integrated with display generating components to form a touch integrated display device, such as a touch screen for a desktop computers, a touch screen for a laptop computer, netbook computers, tablets, web browsers, e-book readers, personal digital assistants (PDAs), smart phones and other similar electronic devices. The display circuitry that is used to update the pixels within the display generate an electrical signal that will interfere with the signals flowing through the traces and sensor electrodes that form part of the capacitive sensing circuitry used to sense the position of an input object. Therefore, it is common to physically separate the display circuitry from the capacitive sensing circuitry to minimize the electrical interference and interaction of the signals flowing through these different types of circuits.
However, with the advent of new touch sensing technologies that include the use of absolute and transcapacitive sensing techniques, the number of sensor electrodes required to perform the touch sensing process has greatly increased, which has also greatly increased the number of traces that need to be routed to the controlling electronics within the touch sensing device. Since it is typical to physically separate the capacitive sensing circuitry from the display updating circuitry, the capacitive sensing circuitry will typically be disposed at the edges of any integrated circuit (IC) chip that contains these two types of electrical circuits to allow the traces used for touch sensing to be routed around or within the border region (i.e., unusable area) of the display panel. Due to the large number of routing traces required for the absolute and/or transcapacitive sensing techniques, the borders of the display need to become excessively large. Alternately, in some cases manufactures will resort to separating the display updating circuitry and the capacitive sensing circuitry into separate IC chips, which greatly increases the piece part and manufacturing cost of the touch sensing device.
Therefore, there is a need for an apparatus and method of forming and using a proximity sensing device that is configured to solve the problems described above. The proximity sensing device also should be inexpensive to produce and be formed so that it can be integrated within a desirably sized electronic system.